Simultaneous whole-field measurements of velocity and concentration fields using a combination of MTV and LIF

A new technique for the simultaneous measurement of velocity and concentration fields is described. We describe here applications in liquid-phase flows, but the methodology can be extended to gas-phase flows with appropriate tracers. In this single-laser, two-tracer approach, molecular tagging velocimetry (MTV) based on the use of a phosphorescent compound is combined with laser induced fluorescence (LIF) using fluorescein as a tracer. Results show that one can design experiments with minimal cross-talk between the LIF and MTV signals. Applications of the simultaneous MTV-LIF technique are demonstrated by performing simultaneous flow visualization and vorticity measurements in a low Reynolds number forced wake and simultaneous velocity-concentration measurements in a turbulent mixing layer. Preliminary data on the mean and RMS fluctuation of velocity and concentration are presented, together with the correlation between velocity and concentration fluctuations.